A small, cylindrical chamber is used in home and office espresso machines to hold a cylindrical capsule or pod containing a measured amount of dry, ground materials used in brewing, such as coffee. The cylindrical chamber, generally made of aluminum foil or heat-resistant plastic, encloses the capsule, and the top and the base of the cylinder are perforated to allow pressurized, heated water to enter the cylinder from the top, flushing axially through the capsule and exiting through the perforated base as an espresso beverage directed from a spout into a receptacle, such as a coffee cup.
Since the espresso preparation procedure involves the use of high pressure water flushing through the brewing materials, such as ground coffee, and this pressure develops very high radial forces on the face of the cylinder envelope, a very rigid, construction is needed to support the capsule and seal the capsule faces during the preparation process. Such rigid construction increases the cost of producing the brewing machine and the cost to the consumer is like-wise higher.
The problem of rigid construction of a capsule for espresso machines also applies to portable brewing systems since the capsule for the dry comestibles need to be held firmly in place on all sides while being subjected to the pressure of heated water applied axially to the capsule and this action produces very high forces both in axial and radial directions.
In U.S. Pat. No. 4,382,402 to Alvarez, for example, the inventor describes a portable coffee maker having a water-heating chamber and a coffee-brewing chamber. This prior art invention has the disadvantage of requiring a rigid support for the separate chambers which adds to the cost of the system.
In U.S. Pat. No. 6,740,345 to Cai, the inventor describes the use of a rigid wall construction of a cartridge which is bulb-shaped and which, dispenses its ingredients when impacted by heated, pressurized water passed axially from an upper, impermeable chamber to the lower one utilizing a through opening in the cartridge. The rigid wall construction of cartridges is more costly to manufacture, as heretofore mentioned, and therefore may result in a product that is expensive when made for one-time use. It also creates greater waste since the sturdier materials tend to be harder on the environment than might be desirable.
In U.S. Pat. No. 6,658,989 to Sweeney el al, the inventor describes a re-usable beverage filter cartridge in a cup-shaped housing provided with dual chambers, closed at the bottom, and having an outlet port. The cartridge is subjected to a stream of heated, pressurized water to mix with the ingredients in a first chamber, and, after passing through a filtering medium, the resultant brew is directed into a second chamber. The disadvantage noted heretofore applies to this cartridge as well, since it is manufactured with a rigid, structure comprising dual chambers.